The present invention is in the field of self-cleaning liners for boilers. More specifically, the invention is directed to a self-cleaning liner, having a thermal protection for a thermal shock resistant sprayhead assembly, capable of spraying either a liquid or a gas, for use in boilers.
In the coal gasification processes a coal slurry is burned in a gasifier. As the coal slurry is burned, it produces a syngas, and quantities of soot, ash, and slag. The syngas and residue is transferred from the gasifier to high pressure boilers which cool the syngas. These boilers generally consist of an outer vessel and an inner tubular liner. The tubular liners in the boilers used in the coal gasification process serve several purposes: they cool the coal gas; they protect the outer vessel walls of the boiler; and, they generate steam. The tubular liners are constructed of a series of tubes joined together by web or fin members such that a cylindrical continuous surface results. Due to this manner of construction the tubular liner has a ribbed contour. As the syngas is passed through the high pressure boilers the soot, ash, and slag residues have a tendency to collect and build up on the ribbed inner surface of the tubular liner.
As the soot, ash and slag build up on the inner surface of the tubular liner the heat transfer capabilities of the liner decreases. This decrease in thermal transfer results in the production of less steam and also the failure to adequately cool the coat syngas to a workable temperature.
Since it is extremely difficult and costly to shut down the boiler and have men enter the vessel to scrape the surface of the tubular liner to remove the residue build-up, various types of cleaning apparatus were devised to remove the residue build-up. Some of these apparatus are incapable of use in high pressure boilers and can only be operated when the boiler is not in use. Thus, although such devices eliminated the need to manually scrape the inner surfaces they still required a costly shutdown of the boiler to clean the liner. Other devices capable of cleaning the liner while the high pressure boiler is in use fail to adequately protect the sprayheads from the thermal shock that occurs when the cleaning medium comes into contact with the hot sprayhead. The few devices that do provide some degree of thermal protection for the sprayhead to keep the temperature differential between the cooling medium and the sprayhead at a minimum, result in a system whereby the thermal protection for the sprayheads cannot be automatically cleaned. Consequently, even with these automatic and semiautomatic cleaners, much time and effort can still be wasted either repairing the sprayheads or cleaning the surfaces f the thermal protection.